Anchorage's soggy and warm winter has been tough on Knobby, a Bactrian camel at the Alaska Zoo, among other animals.

Knobby, a male in the throes of his seasonal rut, has been tracing an icy path as he paces back and forth, staring over the fence at Mary Lu, the zoo's female cold-weather camel. Zookeepers take pains to prevent his enclosure from getting too slippery. "We throw a lot of sand to try to make sure he doesn't hurt himself," said Shannon Jensen, the zoo's curator.

But for creatures of the north without human caretakers, winter rains can be catastrophic.

First reports of the animals' woes came from local Inuit hunters, who months after the rains spotted "confused musk oxen ... wandering out onto the pack ice in search of food, and drifting out to sea on ice pans," according to a study co-authored by Putkonen. The following summer, wildlife officials found emaciated carcasses of animals that had died. The die-off, and the failure of surviving musk oxen to bear calves the following summer, was expected to have long-lasting impacts on the population, the study said.

Climate scientists say a shift to winter rain from snow is likely as the Arctic climate warms and thaws, though there will variations from year to year and location to location.

It's an important subject that has not received enough study, he said. "Most likely, most of the rain-on-snow events have gone unnoticed" -- at least by humans, he said. Even the now-notorious Banks Island musk oxen die-off could have gone undetected without local hunters' reports, he and other researchers have noted. The closest weather station to the musk oxen range was 60 miles away, and it failed to record the heavy rainfall.

Seal, caribou, moose also harmed

Winter rains are taking tolls on other animals in the far north and the ecosystem as a whole. Some recent findings:

• Ice seals will likely be vulnerable to increasing rain, said a 2003 study published in the journal Arctic. The authors, Canadian scientists working on Baffin Island, described a series of spring rains that damaged or destroyed snowy lairs that newborn ringed seals need for shelter. Newborn pups "were left lying on the bare ice," subject to the cold and to much more danger from prowling polar bears and foxes. It adds up to a potential long-term threat to the population. More and more rain -- and resulting damage to conditions needed for pup survival -- was among the justifications cited by the National Oceanic and Atmospheric Administration when, in 2012, it listed ringed and bearded seals as threatened species.

• Vegetation trapped beneath ice can convert into the equivalent of junk food, or worse, for animals that do manage to reach it. Freeze-tolerant Lichen that thrive beneath snow by using little air pockets and air exchanges can die if encased by rain-created ice, said a Norwegian study published in 2011 in the journal Environmental and Experimental Botany. Lichen and mosses are replaced by fungi, some of which hold toxins, Putkonen and his colleagues pointed out in one of their studies.

There is also some indication that freeze-thaw cycles, like those accompanying winter-rain events, increase the toxicity in chokecherries, the fruit of an ornamental species dangerous to moose. The idea of enhanced toxicity was considered after a few Anchorage moose dropped dead almost immediately after eating chokecherries in recent winters. More research is needed on the subject, Alaska Department of Fish and Game officials say.

• Some high-latitude plants in Scandinavia have similar problems, with rain and spurts of warm weather erasing snow cover needed to insulate roots. One study of subarctic shrubs in Sweden, published in the current issue of the journal Plant Biology, found that subarctic shrubs subjected to freeze-thaw icing in January wound up with an 83 percent drop in summer berry production. March icing events, however, did not seem to harm the tested plants, the study said.

• A big winter rainfall in Svalbard in 1995 resulted in the thaw of a wide stretch of permafrost. There was a repeat occurrence there in the winter of 2005-06, when up to half the winter's precipitation was in the form of rain, said a study published in the 2011 issue of The Cryosphere. When that rain comes as downpours, permafrost thaws, the study said. "While small amounts of rain have only minor impact on the ground surface temperature, strong rain events have a long-lasting impact," the study said. Future rains are expected to cause similar damage to other coastal permafrost, said the study.

• Salmon spawning streams in Bristol Bay region stand to be profoundly altered by a shift from winter snow to winter rain, said a study presented at the American Geophysical Union fall conference in December. For now, 70 percent of winter storms occur when temperatures are at or below freezing, but by 2050, that freeze-thaw ratio will flip, with 70 percent expected at above-freezing temperatures, said the study, which used models to predict future hydrology. Affected might be salmon-run timing, quality of spawning grounds and the survival of some subpopulations. Vulnerable subpopulations may have to change or expand spawning grounds, said Dave Albert of the Nature Conservancy's Juneau office, one of the co-authors.

• Heavy rains in summer -- another far-north climate trend -- are killing peregrine falcon chicks in Canada's Nunavut territory, said a study recently published in the journal Global Change Ecology. Rainfall events have increased in the region over the past 30 years, leaving the soaked chicks vulnerable to hypothermia and other dangers. Rainfall was directly to blame for more than a third of the observed nestling deaths.

The rainy trend is not all bad for all animals, however.

For urban moose in Anchorage, the rainfall this winter, and that of recent winters, has been a "mixed bag," said Jessy Coltrane, area wildlife biologist for the Alaska Department of Fish and Game. Like the city's two-legged residents, moose have trouble navigating ice. "I've had to put down moose that have slipped and fallen and broken their pelvis," she said.

Rain and related warm weather also heightens dangers of vehicle-moose collisions, Coltrane said. The rain that washes away snow also removes the white layer that, in normal winter times, provides a visual contrast, she said. Without the snow, dark moose are on dark roadways. "It's not a good combination," she said.

But the rain erases that erases snow drifts clears space for moose to walk and gain access to food from trees and bushes. That vegetation might be more nutritious than the normal winter browse, thanks to the current spring-like conditions, she said. "The sap is probably forming in some trees. I've seen pussy willows," she said.